Collaboration and License Agreements - Contract Balances Narrative (Details) - USD ($) $ in Thousands	6 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Mar. 31, 2022
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue	$ 20,282	$ 28,652
Cost share advance from Pfizer	34,386	$ 38,304
Shared costs	34,386
Cost share advance	0		$ 33,818
Pfizer
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cost share advance from Pfizer	$ 33,800
Reimbursement of total expenses (as a percent)	100.00%
Reimbursement of allowable expenses (as a percent)	50.00%		50.00%
Shared costs	$ 34,400
Accretion of implied financing costs	600
Cost share advance	0
Collaboration expense to Pfizer
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Additions	100,000
Deductions	$ (79,718)